The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus capable of switching between different levels of resolution in a main scanning direction and having a simple configuration.
In a related ink jet recording apparatus, a recording head is moved in the main scanning direction (e.g., the widthwise direction of paper), and ink droplets are jetted from the recording head in synchronism with movement of the recording head. A recording apparatus of this type forms a basic unit pixel by a plurality of ink droplets (e.g. three or four) arranged in the main scanning direction. In this recording apparatus, a drive signal is cyclically and repeatedly generated on a per-print-cycle-basis, wherein a plurality of drive pulses, each pulse having the same waveform pattern, are spaced at constant intervals (meaning that an ink droplet jetted from the actuator as a result of a single waveform being applied to the actuator assumes a substantially constant volume). The drive pulses are arranged in a train and spaced at constant intervals. When a basic unit pixel image is recorded on a recording medium, the drive pulses are selectively supplied to pressure generating elements of the recording head, whereby ink droplets are jetted from the recording head. The recording head employed in the recording apparatus has a row of nozzles formed by arranging a plurality of nozzle orifices in a subscanning direction (e.g., a direction in which paper is to be fed).
In such a recording apparatus, when an attempt is made to perform a recording operation through use of fewer ink droplets required to form an unit pixel, there can be performed a high-resolution recording operation, in which the resolution of an image or character is enhanced with reference to the main scanning direction. In other words, there can be effected switching between a basic mode for effecting recording operation through use of basic unit pixels and a high-resolution mode for effecting recording operation through use of fine unit pixels that are of higher resolution than the basic unit pixels. For instance, in a case where a basic unit pixel to be used in a basic mode consists of four ink droplets, a forward fine unit pixel is formed by combination of the first and second ink droplets, and a rear fine unit pixel is formed by combination of the third and fourth ink droplets. Accordingly, recording can be effected in a high-resolution mode with the level of resolution with respect to the main scanning direction being enhanced to twice that in the basic mode.
However, a recent recording apparatus tends to shorten a single print cycle, in order to improve type speed. Moreover, the number of nozzle orifices constituting the row of nozzles; that is, the number of jetting data sets to be recorded by a single row of nozzles, tends to increase. On one hand, the number of jetting data sets to be recorded within a print cycle increases. On the other hand, setting of the jetting data sets must be performed within a shorter time period. If one dot is recorded in the high-resolution mode; that is, if recording is effected by means of sending data for each fine unit pixel, jetting data must be set within a considerably short time period, thus rendering control of recording operation difficult. Consequently, there must be taken measures to prolong a print cycle within a high-resolution mode or to decrease scanning speed of a carriage, or like measures, thus decreasing the print speed.